Any way.. to check what nessus is doing to detect such vulnerability ?Also I am only resposible for mitigations,Scanning is done by Separate team. How in technical terms i need to investigate the case or what question i need to do o the scanner team. should i ask for any logs....?

you can ask for the full dump of the nessus report. I have a similar problem where scans are run but are uploaded to a reporting system which gives me a whopping 1 line item per vulnerability found and a link to the CVE but not what exactly was found or what triggered it.

When it doubt see if you can run your own scans. I don't always take the word of the people doing our scans. Mostly since they are just using the default safe scan plugins. Not even doing authentication based scans. So it is all just best guess.